Dolphins evolving into groups separated by ocean conditions

We have a very positive view of dolphins - even attributing a smile to them - but new research shows that out at sea groups of dolphins keep themselves very much to themselves and become genetically distinctive.

Conservationists from the Wildlife Conservation Society, the American Museum of Natural History (AMNH), and other conservation and research groups found that currents are among the factors preventing dolphin mixing in the western Indian Ocean.

The study is being published in the journal Hereditary and showcases some new high-tech means of studying marine animals to show how currents and ocean temperatures segregate dolphins.

The Indo-Pacific humpback dolphin was the focus of the study which may reveal how new species evolve because of their environments.

''Examining how environmental factors affect the population structure of marine species is a complex task. Doing this over entire regions is a challenge,'' said lead author Dr. Martin Mendez of the Sackler Institute for Comparative Genomics at the American Museum of Natural History. ''Unlike studies of terrestrial species in easily observable environments, marine species are difficult to follow and the barriers they encounter are often invisible to us. Molecular technologies and remote sensing data can be combined to shed light on these mysteries.''

The scientists used DNA evidence from the dolphins and compared it with satellite data on the state of the oceans.

They found distinct populations of dolphins around Mozambique and Tanzania in Africa, and Oman on the Saudi Arabian peninsula and believe that currents are part of what keeps these groups apart with the South Equatorial Current separating the Mozambique and Tanzania groups.

''With increasing development and potential threats to coastal habitats, understanding the population structure of the Indo-Pacific humpback dolphin in conjunction with environmental factors is an important step in formulating management recommendations and protection measures for the species,'' said Dr. Howard Rosenbaum, Director of the Wildlife Conservation Society's Ocean Giants Program.

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